This invention relates to a platinum electrodeposition bath (suitable for both electroplating & electroforming) which gives a platinum deposit with an attractive shiny granular surface, resembling a velvety texture. This unprecedented surface effect of platinum electrodeposit differentiates from the conventional bright or matte platinum electrodeposits. The term “velvet platinum electrodeposition” is used in this specification to refer to the invention. The present invention provides a new application in decorative uses of platinum electrodeposition.
Platinum electroplating & electroforming have been widely used in the manufacture of ornament and jewelry items, not only because of the bright luster and aesthetic attractiveness of platinum, but also its high chemical inertness. The currently available platinum electrodeposition baths give either bright or matte Pt deposits. For example, in U.S. Pat. No. 5,549,738 & 5,620,583, platinum electrodeposition baths giving bright surface were disclosed. In a very early invention U.S. Pat. No. 1,906,178, it was disclosed that matte Pt electrodeposit was obtained by adjusting the pH of the bath. However, “velvet platinum electrodeposition” has never been reported.
On the contrary, both bright gold electrodeposition and velvet gold electrodeposition are well known in the jewelry industry. The latter is commonly used in the manufacture of hollow statue-like ornaments. Furthermore, bright and velvet silver electrodepositions are also commercially available. The techniques for velvet platinum electrodeposition have never been materialized, so there is a need to develop such technique to satisfy any situation where there is such a need, for example, the jewelry industry.